The invention is directed to a tongue rail device for a grooved rail switch with a tongue rail being displaceable between a stock rail and a switch rail supported by a slide plate and being movable by a setting device.
Usually, the slide plate is joined to the web of the stock and switch rail by weld seams. For increased stability, both of the rails have a supporting seat in the web region in the form of a rolled-in shoulder for a welded-on strip so that the slide plate is positioned on the supporting seat and then welded. The stock rail and the switch rail rest on a base plate and are connected to it by weld seams. Such a design is displayed in German Utility Model No. 69 16 985, FIG. 2.
This design, still in use at the present time, has several disadvantages. For example, special rolled sections are required for the stock rail and the switch rail and these sections are disproportionately expensive, since they are needed only in limited lengths and must be manufactured specially. Since the manufacturer of such special sections can perform the rolling for only a certain minimum quantity, the switch manufacturer must place long-term orders and keep these special sections in stock at great expense.
Another disadvantage of this known design is that the bottom or base plate, to which the stock rail and switch rail are welded, is about 15 mm thick and, accordingly, the tongue or tongue rail is higher by the thickness of the bottom plate than the adjacent track rails. When installing such a switch, the difference in height must be compensated by other construction measures.
The stock rail with the required special rolled shape (type designation BA 75) normally has an average carbon content of 0.6% with the result that welding can be performed only after adequate preheating. Even with preheating and carefully performed welding, there is the danger of an incipient crack in the region of the stock rail at the ends of the bottom plate, because in this region the weld seam exerts a notch effect. There is also the danger that additional cracks will develop due to the inevitable aligning of the tongue rail after welding. Automatic performance of the welding is difficult because of the poor accessibility of the weld seams between the stock or switch rail and the slide plate.
Because of the warpage or distortion that takes place during the welding of such a construction, the cost of installing such a switch is very high. The tongue rail and slide plate must be carefully adapted to one another to ensure a uniform and continuous seating for the tongue rail. Such an operation involves considerable grinding expense.
There are other known tongue rail devices where the slide plate is screwed to the webs of the stock rail and of the switch rail. Such a design is disclosed in the German Patentschrift No. 826 307 and the patent application No. G 15126 V/19a. In such an arrangement there is the disadvantage, particularly if the seating of the stock rail and the switch rail on the track bed is not flat, that the screw connections will loosen in the course of time and safe operation of the switch cannot be assured. Moreover, in this arrangement the inner side of the webs of the stock rail and of the switch rail must be provided with webs or shoulders on which the slide plate can be supported.
Such an arrangement where the parts are screwed together has not been usable in public transportation, such as by streetcar or inter-urban lines.